Methods and compositions for in-situ polymerization reaction to improve shale inhibition

ABSTRACT

A method of modifying an alteration zone of a formation near a wellbore using a non-Newtonian polymeric composition created from a reaction of a non-Newtonian combination comprises the steps of mixing an anhydrous tetraborate and a fluid to create a crosslinker solution, mixing a crosslinkable polyvinyl alcohol and water to create a polymer solution, where the crosslinker solution and the polymer solution form the non-Newtonian combination, pumping the non-Newtonian combination to a reaction zone in the wellbore, where pumping the non-Newtonian combination is configured to induce mixing of the polymer solution and the crosslinker solution, allowing the non-Newtonian combination to react to form the non-Newtonian polymeric composition, allowing the non-Newtonian polymeric composition to migrate to the alteration zone, where the non-Newtonian polymeric composition migrates due to gravity, and allowing the non-Newtonian polymeric composition to interact with the alteration zone to modify the alteration zone.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional Application No.62/187,533 filed on Jul. 1, 2015. For purposes of United States patentpractice, this application incorporates the contents of the ProvisionalApplication by reference in its entirety.

TECHNICAL FIELD

Compositions and methods are provided for modifying the physicalstructure of a formation surrounding a wellbore. More specifically,compositions and methods are provided for forming a polymericcomposition in a wellbore, where the polymeric composition transforms anaspect of the wellbore formation.

BACKGROUND

There are times during drilling operations, when it is necessary toalter the physical structure of a formation surrounding a wellbore.Examples of such physical alterations include fracturing operations,loss circulation control, and shale formation inhibition. Fracturingoperation operations are proactive methods to increase the amount ofhydrocarbons recovered from a formation. Conversely, loss circulationcontrol and shale formation inhibition are defensive measure to preventreductions in recovery.

Loss circulation, a partial or complete loss of drilling fluids into theformation, is a common and expensive problem in drilling operations.Loss circulation causes well control problems and unsafe well controlconditions. When whole volumes of drilling fluids are lost into theformation, additional volumes of drilling fluid must be mixed to make-upfor the losses. Thus, the occurrence of a loss circulation zoneincreases the costs associated with drilling the well and results inlost product time.

Loss circulation occurs due to fractures caused by mud weight/pressure,formations with high permeability and porosity, and natural fractures orcaverns. In complete loss circulation, the wellbore opens and thepressure exerted by the mud column disappears creating an under balancesituation, where the formation fluids enter the wellbore and cause akick.

To combat loss circulation, lost circulation materials are used to plugthe opening in the wellbore. Loss circulation materials can be wholefluids delivered separately to the loss circulation zone, such ascements, or can be fluid additives mixed with the drilling fluids.Conventional fluid additives include chemical reactants and particlesthat are mixed with the mud, such as husks, fibers, or other solids suchas calcium carbonate. Chemical reactants often have delayed reactionpathways, such that the reactants can be mixed in together at thesurface, but the reaction does not proceed until the reactants reach theloss circulation zone.

Problems with current lost circulation materials include cement jobsthat fail to plug the loss circulation zone and compromise the integrityof the casing requiring future remedial work. Solid additives that aretoo small to have effect in large loss zones are also a problem.Chemical reactants that react too quickly or too slowly to plug the losszone are also common problems. Loss circulation materials that requireprecise placement add to the delay time of drilling. Loss circulationmaterials which can be efficiently placed and will act to block theentire loss circulation zone are desired.

Shale formations are commonly encountered during drilling operations.Shale contains clay materials, along with other minerals. Water in thedrilling fluids interacts with the shale to cause shale swelling,sloughing, and can even lead to well collapse. The shale absorbs waterfrom the drilling fluids and increases in weight and dimension. By someestimates, 70 percent (%) of wellbore instabilities are associated withshale formations. The instabilities pose safety risks and increase wellcosts.

Shale swelling is usually addressed by adding shale inhibitor materialsto the drilling fluids at the surface, the inhibitors interrupt theinteraction between the shale and the water. The drilling fluids withshale inhibitor materials are then pumped to the thief zones to preventthe shale swelling. Inhibitor materials are expensive. Additionally,inhibitor materials have environmental limitations and pose problems fordisposal.

Conventional methods of addressing loss of circulation and shaleformations use different treatment systems. These different treatmentsystems incur costs and can take time to change back and forth betweenthe two.

Therefore, a product that alters the physical structure of the formationwithout such drawbacks is desired.

SUMMARY

Compositions and methods are provided for modifying the physicalstructure of a formation surrounding a wellbore. More specifically,compositions and methods are provided for forming a polymericcomposition in a wellbore, where the polymeric composition transforms anaspect of the wellbore formation.

In one aspect, a method of modifying an alteration zone of a formationnear a wellbore using a non-Newtonian polymeric composition created froma reaction of a non-Newtonian combination is provided. The methodincludes the steps of mixing an anhydrous tetraborate and a fluid tocreate a crosslinker solution, mixing a crosslinkable polyvinyl alcoholsolution and a polyvinyl acetate solution to create a polymer solution,where the crosslinker solution and the polymer solution form thenon-Newtonian combination, pumping the non-Newtonian combination to areaction zone in the wellbore, where the pumping of the non-Newtoniancombination is configured such that the crosslinker solution is isolatedfrom the polymer solution until the reaction zone, the reaction zonebeing defined as a point which allows the reaction between thecrosslinker solution and the polymer solution to proceed to a completiontime prior to reaching the alteration zone, the completion time beingdefined as the time to react substantially all of the crosslinkersolution and the polymer solution, where pumping the non-Newtoniancombination is configured to induce mixing of the polymer solution andthe crosslinker solution, where a rate of dissolution of the polymersolution depends on the temperature in the reaction zone, allowing thenon-Newtonian combination to react to form the non-Newtonian polymericcomposition, allowing the non-Newtonian polymeric composition to migrateto the alteration zone, where the non-Newtonian polymeric compositionmigrates due to gravity, and allowing the non-Newtonian polymericcomposition to interact with the alteration zone to modify thealteration zone.

In certain aspects, the alteration zone is a loss circulation zone witha loss of circulation. In certain aspects, the non-Newtonian polymericcomposition molds to the shape of the loss circulation zone forming aseal which controls the loss of circulation in the loss circulationzone. In certain aspects, the alteration zone is a shale formation. Incertain aspects, a ratio of anhydrous sodium tetraborate to thecrosslinkable polyvinyl alcohol is 1:3 and 1:5. In certain aspects, aconcentration of anhydrous sodium tetraborate in the crosslinkersolution is between 0.1 percent by volume (% by volume) and 1.5% byvolume. In certain aspects, a blend ratio of polyvinyl acetate topolyvinyl alcohol in the polymer solution is 45 to 1. In certainaspects, the reaction zone is at the distance from the alteration ofbetween 200 feet and 500 feet. In certain aspects, the completion timeis less than 30 minutes after contact in the reaction zone. In certainaspects, the fluid is a drilling fluid. In certain aspects, the drillingfluid is an aqueous-based drilling mud. In certain aspects, thealteration zone is indicated by a pressure drop in the wellbore.

In a second aspect, a non-Newtonian combination for reacting to create anon-Newtonian polymeric composition in situ in a wellbore is provided.The non-Newtonian combination includes a crosslinker solution operableto undergo a reaction to crosslink a crosslinkable polymer in thewellbore, the crosslinker solution including anhydrous sodiumtetraborate and a drilling fluid, where the reaction is operable toproceed to a completion point, a polymer solution operable to form thenon-Newtonian polymeric composition in the wellbore when brought intocontact with the crosslinker solution, the polymer solution includingthe crosslinkable polymer and water, the crosslinkable polymer includingpolyvinyl alcohol and polyvinyl acetate.

In certain aspects, the completion point occurs less than 30 minutesafter contact between the crosslinker solution and the polymer solution,the contact occurring in the wellbore. In certain aspects, a ratio ofanhydrous sodium tetraborate to the crosslinkable polyvinyl alcohol isbetween 1:3 and 1:5. In certain aspects, a concentration of anhydroussodium tetraborate in the crosslinker solution is between 0.1% and 1.5%by volume of the crosslinker solution. In certain aspects, a blend ratioof the polyvinyl acetate to polyvinyl alcohol is 45 to 1. In certainaspects, the drilling fluid is an aqueous-based drilling mud.

In a third aspect, a non-Newtonian combination includes anhydrous sodiumtetraborate operable to crosslink polyvinyl alcohol, the anhydroussodium tetraborate being present in a concentration between 0.1% and1.5% by volume of the non-Newtonian combination, polyvinyl alcoholoperable to form a crosslinked polymer, the polyvinyl alcohol beingpresent in a concentration between 0.4% and 6% by volume, and polyvinylacetate.

In certain aspects, the completion point occurs less than 30 minutesafter contact between the anhydrous sodium tetraborate and the polyvinylalcohol. In certain aspects, a ratio of anhydrous sodium tetraborate topolyvinyl alcohol is 1:3 and 1:5. In certain aspects, the anhydroussodium tetraborate is mixed with a drilling fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of embodiments willbecome better understood with regard to the following descriptions,claims, and accompanying drawings. It is to be noted, however, that thedrawings illustrate only several embodiments and are therefore not to beconsidered limiting of the inventive scope as it can admit to otherequally effective embodiments.

FIG. 1 is a pictorial representation of the twisting of thenon-Newtonian polymeric composition.

FIG. 2 is a pictorial representation of the stretching capability of thenon-Newtonian polymeric composition.

FIG. 3 is a pictorial representation of the stretching capability of thenon-Newtonian polymeric composition.

FIG. 4 is a pictorial representation of the stretching capability of thenon-Newtonian polymeric composition.

FIG. 5 is a pictorial representation of the non-Newtonian polymericcomposition.

FIG. 6 is a pictorial representation of the non-Newtonian polymericcomposition.

FIG. 7 is a pictorial representation of the swelling property of thenon-Newtonian polymeric composition.

FIG. 8 is a pictorial representation of reaction between chains ofpolyvinyl alcohol and the borate ion.

FIG. 9 is a graph of the differential pressure of a shale plug and acoated shale plug.

FIGS. 10a-c are pictorial representations of a shale plug that is coatedon one end with the non-Newtonian polymeric composition.

FIG. 11 is a graph of the change in weight of a shale plug and a coatedshale plug that have been immersed in brine.

DETAILED DESCRIPTION

While the following detailed description will contain severalembodiments, it is understood that one of ordinary skill in the relevantart will appreciate that many examples, variations and alterations tothe apparatus and methods described are within the scope and spirit ofthe embodiments. Accordingly, the embodiments described are set forthwithout any loss of generality, and without imposing undue limitations.

The non-Newtonian polymeric composition is a material created in situ inthe wellbore to modify an alteration zone. The non-Newtonian polymericcomposition has distinctive properties: it stretches easily withoutbreaking, takes the form of its container, acts as a barrier to water,and swells like a balloon if gas is blown inside it. The non-Newtonianpolymeric composition is created from the non-Newtonian combination. Thenon-Newtonian combination includes the crosslinker solution and thepolymer solution.

As used throughout, “alteration zone” refers to any area of a formationthat requires treatments to improve wellbore or formation stability.Alteration zones can include loss circulation zones, shale formationzones, and combinations thereof.

As used throughout, “alteration event” refers to when the alterationzone is entered or encountered during drilling operations. An alterationevent is signaled by a drop in pressure in the wellbore.

The crosslinker solution crosslinks the crosslinkable polymer. Examplesof crosslinker solutions include crosslinking agents such as aluminumcontaining compounds, antimony containing compounds, zirconiumcontaining compounds, titanium containing compounds, and boroncontaining compounds. In at least one embodiment, the boron containingcompound is sodium tetraborate. In at least one embodiment, thecrosslinker solution is a sodium tetraborate (borax) solution. The boraxsolution is created by mixing anhydrous sodium tetraborate (Na₂B₄O₇)with a fluid. The anhydrous sodium tetraborate can be any commerciallyavailable anhydrous sodium tetraborate. In certain embodiments, theborax solution is created by mixing hydrate forms of sodium tetraboratewith the fluid. Hydrate forms of sodium tetraborate include thepentahydrate form (Na₂B₄O₇.5H₂O) and the decahydrate form(Na₂B₄O₇.10H₂O). The fluid can be any fluid capable of mixing withanhydrous sodium tetraborate to create the borax solution and of beinginjected into the wellbore. Examples of fluids include water, brine, andaqueous-based drilling fluids. In at least one embodiment, the fluid isan aqueous-based drilling mud. In at least one embodiment, the fluid isthe same aqueous-based drilling fluid being used to drill the wellboreat the time of the alteration event. In at least one embodiment, theborax solution is created by stirring the anhydrous sodium tetraborateinto the fluid. In at least one embodiment, mixing of the anhydroussodium tetraborate and the fluid is achieved with the use of anagitator. In certain embodiments, the anhydrous sodium tetraborate ismixed with the fluid on site at the time of the alteration event. In atleast one embodiment, the anhydrous sodium tetraborate is mixed with thefluid prior to the alteration event. In at least one embodiment of thepresent invent, the anhydrous sodium tetraborate is mixed with the fluidin a hopper system. In at least one embodiment, the mixing occurs in acement truck. In at least one embodiment, the anhydrous sodiumtetraborate is pumped downhole to the alteration zone and is mixed withthe aqueous-based drilling fluid using a downhole agitator tool. In atleast one embodiment, the borax solution is created off site from wherethe wellbore is being drilled. In at least one embodiment, excessanhydrous sodium tetraborate mixed with the fluid remains in the fluid.In embodiments where the fluid is an aqueous-based drilling fluid,anhydrous sodium tetraborate present in the aqueous-based drilling fluiddoes not change the efficacy of the aqueous-based drilling fluid. Whenthe non-Newtonian polymeric composition is needed, the concentration ofthe polymer solution can be narrowly tailored to produce the reaction atthe desired reaction rate to produce the non-Newtonian polymericcomposition with the desired properties.

The concentration of the anhydrous sodium tetraborate in the boraxsolution is between about 0.1% by volume of the borax solution and about1.5% by volume of the borax solution. The concentration of anhydroussodium tetraborate in the borax solution is dependent on the type offluid used, the temperature and pressure of the wellbore, and the mixingstrength. As used throughout, “mixing strength” refers to how thoroughlyor vigorously the borax solution is mixed. In at least one embodiment,the mixing strength of the borax solution refers to high shear mixing ofthe borax solution. The concentration of anhydrous sodium tetraborate inthe borax solution effects the viscosity of the non-Newtonian polymericcomposition. In at least one embodiment, the dissolution of theanhydrous sodium tetraborate in the borax solution occurs at surfacetemperatures. A greater rate of dissolution increases the spread ofborate ion (B(OH)₄ ⁻) in solution which increases the crosslinking ofthe crosslinkable polymer. The total volume of the borax solutiondepends upon the nature of the alteration zone. For example, the largerthe alteration zone encountered, the more borax solution is needed. Inat least one embodiment, the total volume of the borax solution can bein the range from about 10 barrels to about 100 barrels. In at least oneembodiment, the total volume of borax solution mixed for pumping intothe wellbore is 50 barrels.

The polymer solution contains the crosslinkable polymer that forms thenon-Newtonian polymeric composition on contact with the crosslinkersolution.

In at least one embodiment, the polymer solution is a polyvinyl blendsolution, where the crosslinkable polymer is a mixture of polyvinylalcohol (PVA) and polyvinyl acetate (PVAc). The polyvinyl blend iscreated by mixing a polyvinyl alcohol (PVA) solution and polyvinylacetate (PVAc) solution in a blend ratio of PVAc to PVA. The blend ratioof PVAc to PVA in the polyvinyl blend solution is 45 to 1 by volume. Thepolyvinyl blend is crosslinkable.

The PVA solution is created by mixing powdered polyvinyl alcohol withhot water. The powdered polyvinyl alcohol can be any commerciallyavailable powdered polyvinyl alcohol ((C₂H₄O)_(x)). In a preferredembodiment, distilled water is used to create the PVA solution. Mixingcontinues until all of the polyvinyl alcohol is dissolved. In at leastone embodiment, the PVA solution is created by stirring the polyvinylalcohol and the water. In at least one embodiment, the powderedpolyvinyl alcohol is mixed with the water prior to the alteration event.In at least one embodiment, the powdered polyvinyl alcohol is mixed withthe water at the time of the alteration event. In at least oneembodiment, the PVA solution is created off site from where the wellboreis being drilled. In at least one embodiment, the PVA solution is acommercially available PVA solution. The concentration of the polyvinylalcohol in the PVA solution is between about 0.4% by volume of PVAsolution and about 6.0% by volume of PVA solution. The concentration ofthe PVA solution is dependent on the temperature and pressure of thewellbore. The rate of dissolution of polyvinyl alcohol depends ontemperature. At increased temperatures a greater rate of polyvinylalcohol dissolution in the water occurs to create the PVA solution,which results in a more homogenous final non-Newtonian polymericcomposition. The polyvinyl alcohol is added to the water at an additiontemperature and mixed until the polyvinyl alcohol is dispersed. The PVAsolution is then heated to a dissolution temperature and mixed until thepolyvinyl alcohol is dissolved. The addition temperature is betweenabout 15 degrees Celsius (° C.) and about 55° C., alternately betweenabout 20° C. and about 50° C., alternately between about 30° C. andabout 40° C. The dissolution temperature is between about 70° C. andabout 100° C., alternately between about 75° C. and about 95° C., andalternately between about 80° C. and about 90° C. In at least oneembodiment, polyvinyl alcohol is added to water at an additiontemperature of about 20° C. and mixed until the polyvinyl alcohol isdispersed. After the polyvinyl alcohol is fully dispersed, thetemperature is increased to a constant dissolution temperature of about80° C. with constant mixing until the polyvinyl alcohol is fullydissolved. In at least one embodiment, the dissolution temperature is90° C.

The PVAc solution is created by mixing powered polyvinyl acetate withmethanol. The PVAc can be any commercially available powered polyvinylacetate. The concentration of the polyvinyl acetate in the PVAc solutionis 53% by weight in methanol. Mixing continues until all of thepolyvinyl acetate is dissolved. In at least one embodiment, thepolyvinyl acetate is mixed with methanol prior to the alteration event.In at least one embodiment, the powdered polyvinyl acetate is mixed withthe methanol at the time of the alteration event.

In at least one embodiment, the polymer solution is mixed in a vesselafter the alteration event in a vessel near the wellbore, prior to beingplaced into the wellbore, as this ensures thorough mixing.

The polymer solution can include additives. Examples of additivesinclude starch, emulsifier, and clay. The additives can increase thepourability and flexibility of the non-Newtonian polymeric composition.In at least one embodiment, the polymer solution includes starch as anadditive.

The total volume of the polymer solution depends upon the nature of thealteration zone. For example, the larger the alteration zoneencountered, the more polymer solution is needed. In at least oneembodiment, the total volume of polymer solution can be in the rangefrom about 10 barrels to about 100 barrels. In at least one embodiment,the total volume of the polymer solution is 50 barrels. In at least oneembodiment, where the polymer solution is a polyvinyl blend solution,the total volume of the polyvinyl blend solution is 50 barrels.

The concentrations of the polymer solution and crosslinker solution andthe ratio of the polymer solution to the crosslinker solution produce anon-Newtonian polymeric composition having the properties desired. In atleast one embodiment, maintaining the ratio of borate ions to polyvinylions is critical to achieving a non-Newtonian polymeric composition withthe desired properties. The desired concentrations are determined basedon the suspected size of the alteration zone in the absence ofconsiderations of environmental impact because the non-Newtonianpolymeric composition is environmentally friendly, the need for excessreactant, or which reactant is calculated first. The final concentrationof the total volume of the crosslinker solution and the total volume ofthe polymer solution must be calculated to maintain a ratio of sodiumtetraborate to polyvinyl alcohol in the range of between about 1:3 toabout 1:5. In at least one embodiment, the ratio of sodium tetraborateto polyvinyl alcohol is 1:4. At a ratio of sodium tetraborate topolyvinyl alcohol of 1:4 neither component is in excess.

The non-Newtonian polymeric composition formed from the reaction of thenon-Newtonian combination, specifically the crosslinker solution and thepolymer solution is a network of cross-linked chains that traps waterand produces a gel. Sources for the trapped water include water from theaqueous-based drilling fluid and water from the non-Newtoniancombination. The aqueous drilling fluid can mix with the crosslinkersolution, the polymer solution, or combinations thereof before thereaction that forms the non-Newtonian polymeric composition. Thereaction between the crosslinker solution and the polymer solutioninitiates at a rapid rate. The reaction between the crosslinker solutionand polymer solution occurs in between about 1 and about 5 minutes,alternately between about 1 and about 4 minutes, alternately betweenabout 1 and about 3 minutes, and alternately between about 1 and about 2minutes. The reaction occurs in the absence of special reactionconditions. The reaction to form the non-Newtonian polymeric compositionoccurs in the absence of heating, catalysts, pressure, and extendedtime. Without being bound to a particular theory, it is believed thatthe mass of the non-Newtonian polymeric composition will twist and turnas hydrogen bonds form between the hydroxyl groups (—OH) on the borateions and the hydrogen of the hydroxyl groups of the polyvinyl alcohol,see FIG. 8. The non-Newtonian polymeric composition stretches, conformsto the shape of its container, is waterproof, and swells like a balloonif a gas is blown into the non-Newtonian polymeric composition, seeFIGS. 1-7.

In a method to alter an alteration zone of a formation, thenon-Newtonian combination described forms the non-Newtonian polymericcomposition when brought into contact in situ in the wellbore, where thereaction occurs to modify the alteration zone. Advantageously, thenon-Newtonian polymeric composition is effective because it is stickytowards the rock surface and therefore more adhesive to cure thealteration event.

After obtaining the crosslinker solution and the polymer solution, thenon-Newtonian combination is delivered to the reaction zone in thewellbore. The reaction zone is the point in the wellbore where thereaction of the non-Newtonian combination is initiated. The reactionzone can be at the alteration zone or can be at a distance before thealteration zone. Being at a distance before the alteration zone allowsthe non-Newtonian combination to migrate from the reaction zone to thealteration zone while reacting, so that the reaction between thecrosslinker solution and the polymer solution proceeds to the completionpoint prior to reaching the alteration zone. In accordance with at leastone embodiment, the reaction zone occurs in the range from about 50 feetto about 1000 feet before the alteration zone, alternately from about100 feet to about 800 feet before the alteration zone, or alternatelyfrom about 200 feet to about 500 feet before the alteration zone. Thereaction zone is defined based on the total volume of the non-Newtoniancombination, the size of the alteration zone, and the temperature andpressure conditions in the wellbore. The completion point is the pointin time at the end of the completion time. The completion time is thetime it takes to react all or substantially all of the crosslinkersolution and the polymer solution to create the non-Newtonian polymericcomposition. The completion time is less than about 60 minutes,alternately less than about 30 minutes, alternately less than about 20minutes, alternately less than about 10 minutes, alternately less thanabout 5 minutes, alternately less than about 4 minutes, alternately lessthan about 3 minutes, alternately less than about 2 minutes, oralternately less than about 1 minute. In at least one embodiment, thecompletion time is less than 30 minutes after the non-Newtoniancombination makes contact in the reaction zone.

The non-Newtonian combination is delivered to the reaction zone by anyknown means capable of delivering a fluid from the surface to a depth ofthe wellbore, such that the crosslinker solution is isolated from thepolymeric solution until the reaction zone. Examples of means fordelivering the non-Newtonian combination to a depth of the wellboreinclude any manner in which drilling fluid can be delivered into thewellbore. Examples of means for delivering a drilling fluid to awellbore include coiled tubing, open-end drill piping, piping andthrough the casing. In at least one embodiment, the non-Newtoniancombination is delivered to the reaction zone via coil tubing runs. Inat least one embodiment, the polymer solution is delivered through thecasing in the wellbore in any manner in which drilling fluid isdelivered into the wellbore, such as piping.

The order in which the polymeric solution and the crosslinker solutionare delivered to the reaction zone does not affect the reaction betweenthe two or the properties of the non-Newtonian polymeric composition. Inat least one embodiment, the polymer solution is delivered to thereaction zone after the entire volume of the crosslinker solution isdelivered to the reaction zone. In at least one embodiment, thecrosslinker solution is delivered to the reaction zone after the entirevolume of the polymer solution is delivered to the reaction zone. In atleast one embodiment, the crosslinker solution and the polymer solutionare delivered to the reaction zone during the same time frame, byseparate piping systems, such as an open-ended drill pipe or coiltubing. The non-Newtonian combination is not delivered to the reactionzone by the same piping system at the same time. The method to alter analteration zone of a formation is in the absence of the non-Newtoniancombination being mixed on a surface and pumped to the reaction zonetogether. By delivering the crosslinker solution and polymer solutionseparately to the reaction zone, the reaction is delayed, which ensuresthat the completion point is reached at or near the alteration zone andavoids blocking fractures or other points in the wellbore that shouldnot be blocked.

The pumping of the non-Newtonian combination occurs at a rate thatinduces mixing of the polymer solution and the crosslinker solution inthe reaction zone. The mixing of the polymer solution with thecrosslinker solution provides the necessary contact between the polymersolution and the crosslinker solution to form the non-Newtonianpolymeric composition. The reaction fails to proceed at temperaturesabove 120° C. and alternately above 150° C.

After delivery of the non-Newtonian combination to the reaction zone,the crosslinker solution and the polymer solution react to form thenon-Newtonian polymeric composition. In at least one embodiment, thenon-Newtonian combination reacts in the reaction zone. In at least oneembodiment, the non-Newtonian combination reacts while migrating fromthe reaction zone to the alteration zone. In at least one embodiment,the time it takes for the reacting non-Newtonian combination to migratefrom the reaction zone is less than the completion time. Thenon-Newtonian combination migrates due to gravity. In at least oneembodiment, the non-Newtonian polymeric composition forms in one mass.

When the alteration zone is a loss circulation zone, the non-Newtonianpolymeric composition operates to control the loss of circulation. In atleast one embodiment, the non-Newtonian polymeric composition molds tothe shape of the loss circulation zone forming a seal. The seal controlsloss circulation. In at least one embodiment, the non-Newtoniancombination forms a mesh-like consistency that attaches to the rock ofthe wellbore and plugs the loss circulation zone minimizing the fluidloss.

When the alteration zone is a shale formation, the non-Newtonianpolymeric composition operates to prevent the interaction between shaleand water. In at least one embodiment, the non-Newtonian polymericcomposition adheres to a shale formation preventing the interaction ofwater in the aqueous drilling fluid and the shale. The non-Newtonianpolymeric composition prevents the swelling of the shale formations andthe dispersion of shale into the drilling fluid. Without being bound toa specific theory, it is believed that the non-Newtonian polymericcomposition plugs pores of a shale formation by forming a thin film. Aportion of the non-Newtonian polymeric composition can adhere to thesurface of the shale formation, while the remaining mass of thenon-Newtonian polymeric composition can slide or move on finding otherpoints of the shale formation to adhere on to, thus forming a film froma mass of the non-Newtonian polymeric composition. It is understood thatthe adhesion of the non-Newtonian polymeric composition to the shale isfacilitated by the fact that shale is hydrophilic and thus is attractedto the water in the non-Newtonian polymeric composition. The water thatwould otherwise interact with the shale is encapsulated in thecross-linked polymer of the non-Newtonian polymeric composition.

EXAMPLES Example 1

A PVA solution of 4% by weight polyvinyl alcohol was prepared byweighing 40 g of powdered polyvinyl alcohol and adding it to 1 Ldistilled water at 50° C. The PVA solution was then heated to 90° C.until the polyvinyl alcohol was completely dissolved. The PVA solutionwas mixed with a PVAc solution to create a polymer solution and maintaina blend ratio of PVAc to PVA of 45 to 1. A borax solution of 4% byweight borax was prepared by weighing 40 g anhydrous sodium tetraborateand stirring it into 1 L distilled water. To create the non-Newtonianpolymeric composition, 100 mL of the borax solution was added to 400 mLof the polymer solution. Within seconds a white polymeric substance wasformed. The polymer formed on the end of the stirrer and began to twistand turn. Without being bound to a particular theory, it is believedthat the strands twisted and turned as hydrogen bonds formed between thehydroxyl groups (—OH) on the borate ions and the polyvinyl alcohol. Atthis point, the non-Newtonian polymeric composition was ready and couldbe isolated from its liquid media. The non-Newtonian polymericcomposition stretches, conforms to the shape of its container, iswaterproof, and swells like a balloon if a gas is blown into thenon-Newtonian polymeric composition, see FIGS. 1-7.

Example 2

The ability of the non-Newtonian polymeric composition to adhere to andencapsulate shale was tested. The first test tested a differentialpressure test in a core flood system of a shale plug. The shale plugalong was found to have a pressure drop of about 200 psi. A sample ofthe non-Newtonian polymeric composition of Example 1 was coated aroundone end of the shale plug. The non-Newtonian polymeric composition wasallowed to dry on the end of the shale plug, see FIG. 10. The coatedshale plug was tested and found to have a pressure drop of about 1600psi. The increased pressure drop in the shale plug coated with thenon-Newtonian polymeric composition shows the impermeable film that thenon-Newtonian polymeric composition forms that prevented the flow offluids from one end of the coated plug to the other end, see FIG. 9.

In a second test, a shale plug was weighed and the dimensions weremeasured. The shale plug was then submerged in 10% brine solution forthree hours. The shale plug was removed from the brine and re-weighedand the dimensions were again measured. The test was repeated for ashale plug coated entirely in the non-Newtonian polymeric composition.After being submerged for three hours, the coated shale plug showed nochange in weight or dimensions. The results indicate that thenon-Newtonian polymeric composition inhibited the shale plug andprevented water molecules from invading the shale plug, see FIG. 11.

Example 3

After a loss circulation zone is discovered, 50 barrels of 4% by volumeborax solution would be mixed with an additional 2000 barrels ofdrilling mud at the surface using an agitator at low speed. Theresulting 50 barrels of borax solution have a concentration of 0.1% byvolume borax solution. A pill of 50 barrels of the 0.1% by volume boraxsolution would then be pumped to the reaction zone.

At the same time, 50 barrels of 4% by volume PVA solution is injectedthrough a separate drill pipe to the reaction zone. In this case, thereaction zone is 500 feet uphole of the loss circulation zone. It ispredicted that within 30 minutes, the pressure in the wellbore willreturn to pre-loss circulation levels, indicating that the non-Newtonianpolymeric composition has sealed all or substantially all of the losscirculation zone.

Although the present embodiments have been described in detail, itshould be understood that various changes, substitutions, andalterations can be made hereupon without departing from the principleand scope of the embodiments. Accordingly, the scope of the embodimentsshould be determined by the following claims and their appropriate legalequivalents.

The singular forms “a,” “an,” and “the” include plural referents, unlessthe context clearly dictates otherwise.

Optional or optionally means that the subsequently described event orcircumstances can or may not occur. The description includes instanceswhere the event or circumstance occurs and instances where it does notoccur.

Ranges may be expressed as from about one particular value to aboutanother particular value. When such a range is expressed, it is to beunderstood that another embodiment is from the one particular value tothe other particular value, along with all combinations within saidrange.

As used here and in the appended claims, the words “comprise,” “has,”and “include” and all grammatical variations thereof are each intendedto have an open, non-limiting meaning that does not exclude additionalelements or steps.

As used here, terms such as “first” and “second” are arbitrarilyassigned and are merely intended to differentiate between two or morecomponents of an apparatus. It is to be understood that the words“first” and “second” serve no other purpose and are not part of the nameor description of the component, nor do they necessarily define arelative location or position of the component. Furthermore, it is to beunderstood that that the mere use of the term “first” and “second” doesnot require that there be any “third” component, although thatpossibility is contemplated under the scope of the embodiments.

What is claimed is:
 1. A method of modifying an alteration zone of aformation near a wellbore using a non-Newtonian polymeric compositioncreated from a reaction of a non-Newtonian combination, the methodcomprising the steps of: mixing an anhydrous sodium tetraborate and afluid to create a crosslinker solution, wherein a concentration ofanhydrous sodium tetraborate in the crosslinker solution is between 0.1%and 1.5% by volume: mixing a crosslinkable polyvinyl alcohol solutionand a polyvinyl acetate solution to create a polymer solution, wherein ablend ratio of polyvinyl acetate to polyvinyl alcohol in the polymersolution is 45 to 1, wherein the crosslinker solution and the polymersolution form the non-Newtonian combination, wherein a ratio ofanhydrous sodium tetraborate to the crosslinkable polyvinyl alcohol inthe non-Newtonian combination is between 1:3 and 1:5; delivering thenon-Newtonian combination to a reaction zone in the wellbore, whereindelivering the non-Newtonian combination is configured such that thecrosslinker solution is isolated from the polymer solution until thereaction zone, the reaction zone being defined as a point which allowsthe reaction between the crosslinker solution and the polymer solutionto proceed to a completion time prior to reaching the alteration zone,the completion time being defined as the time to react the crosslinkersolution and the polymer solution, wherein delivering the non-Newtoniancombination is configured to induce mixing of the polymer solution andthe crosslinker solution, wherein a rate of dissolution of the polymersolution depends on the temperature in the reaction zone; allowing thenon-Newtonian combination to react to form the non-Newtonian polymericcomposition; allowing the non-Newtonian polymeric composition to migrateto the alteration zone, wherein the non-Newtonian polymeric compositionmigrates due to gravity; and allowing the non-Newtonian polymericcomposition to interact with the alteration zone to modify thealteration zone.
 2. The method of claim 1, wherein the alteration zoneis a loss circulation zone with a loss of circulation.
 3. The method ofclaim 2, wherein the non-Newtonian polymeric composition molds to theshape of the loss circulation zone forming a seal which controls theloss of circulation in the loss circulation zone.
 4. The method of claim1, wherein the alteration zone is a shale formation.
 5. The method ofclaim 1, wherein the reaction zone is at the distance from thealteration zone of between 200 and 500 feet.
 6. The method of claim 5,wherein the alteration zone is indicated by a pressure drop in thewellbore.
 7. The method of claim 1, wherein the completion time is lessthan 30 minutes after contact in the reaction zone.
 8. The method ofclaim 1, wherein the fluid is a drilling fluid.
 9. The method of claim8, wherein the drilling fluid is an aqueous-based drilling mud.
 10. Themethod of claim 1, wherein the step of delivering the non-Newtoniancombination to a reaction zone in the wellbore occurs via coil tubingruns.